Direct synthesis of faujasite zeolites containing sodium and lithium

ABSTRACT

LITHIUM-CONTAINING FAUJASITES ARE PRODUCED WITHOUT THE NECESSITY OF AN ION EXCHANGE STEP. A GEL IS FIRST FORMED OF AN ALUMINOSILICATE CONTAINING ALL OF THE ALUMINA REQUIRED FOR THE CRYSTALLIZATION MIXTURE. THE GEL IS THEN MODIFIED BY THE ADDITION OF REACTIVE SILICA AND, IF NECESSAY, OTHER COMPONENTS TO YIELD SPECIFIED MOLAR RATIOS RE LATING TO AL2O3, SIO2, NA2O, LI2O AND H2O VALUES. THE RESULTANT CRYSTALLIZATION MIXTURE IS TREATED TO CRYSTALLIZE OUT THE LITHIUM-CONTAINING FAUJASITE.

3,798,311 DIRECT SYNTHESIS OF FAUJASITE ZEOLITES CONTAINING SODIUM ANDLITHIUM Jean-Louis Guth, Mulhouse, Albert Pereyron, Brunstatt, andRaymond Wey, Mnlhouse, France, assignors to Azote et Produits ChimiquesS.A.

No Drawing. Filed Sept. 20, 1971, Ser. No. 182,204 Claims priority,application France, Sept. 18, 1970, 7033911; Mar. 10, 1971, 7108244 Int.Cl. C01b 33/28 US. Cl. 423-629 15 Claims ABSTRACT OF THE DISCLOSURELithium-containing faujasites are produced without the necessity of anion exchange step. A gel is first formed of an aluminosilicatecontaining all of the alumina required for the crystallization mixture.The gel is then modified by the addition of reactive silica and, ifnecessay, other components to yield specified molar ratios relating toA1 SiO Na O, Li O and H 0 values. The resultant crystallization mixtureis treated to crystallize out the lithium-containing faujasite.

CROSS REFERENCE TO RELATED APPLICATION This invention is related toapplicants application Ser. No. 178,794 filed Sept. 8, 1971, entitledPreparation of =Faujasite-Type Zeolites and the disclosure of saidapplication is incorporated by reference herein.

BACKGROUND OF THE INVENTION This invention relates to a novel processfor the preparation of zeolites of the faujasite type containing bothsodium and lithium cations and to the zeolites prepared by this process.

Zeolites are crystallized aluminosilicates having a threedimensionalframework of SiO.; and A tetrahedra in which every oxygen atom is sharedby two adjacent tetrahedra. The negative charges of the A10 tetrahedraare balanced by alkali metal or alkaline-earth metal cations. Since thearrangement of SiO., and A10 tetrahedra is regular, the zeolitestructure comprises large cavities which are connected by channelscontaining water and balancing cations. After dehydration or activation,the zeolites selectively adsorb molecules having a dimension compatiblewith the size of the channels. Owing to this characteristic, zeoliteshave been called molecular sieves.

The zeolites have the following general formula:

M O, A1 0 YSiO zH 0 where M is one or several metal cations, n is theirvalence and Y and 2 represent the number of moles of SiO and H 0respectively.

The present invention, in particular, relates to a process for thepreparation of a faujasite type zeolite, i.e., having a face-centeredcubic lattice, a parameter a ranging between 24.5 and 25 A., a structureof stacked cubic octahedra and hexagonal prisms as illustrated forexample in Information Chimie, No. 76 (October 1969), p. 33, andcontaining Na+ and Li+ cations. As already known, the presence of Li+cations in zeolites brings about numerous advantages. Lithium cationsare more easily exchangeable than, for example sodium cations;therefore, less contacts are necessary to obtain a given rate ofexchange. Furthermore, faujasites containing Na+ and Li+ can advantageously be used for preparing catalysts by exchanging Li+ by La,rare-earth metals, etc. Still further, the presence of litium cations ina faujasite permits selective adsorptions, such as the adsorption ofnaphthenic compounds, for example.

Heretofore, faujasites containing Na+ and Li+ were United States Patent0 3,798,311 Patented Mar. 19, 1974 prepared by a two step process. In afirst step a faujasite containing only Na+ cations was prepared frommixtures containing SiO A1 0 Na O and H 0 and then in a second step allof the lithium cations were introduced by ion exchange. Though there hasbeen proposed a direct synthesis process for preparing a zeolitecontaining lithium:ZMS-3 zeolite, it has a different structure than thefaujasite of the present invention, a hexagonal axis of symmetry, inparticular, G. T. Kokotailo and I. Ciric (Second InternationalConference on Molecular Sieve Zeolites; Sept. 8-11, 1970, Worcester,Mass.).

SUMMARY OF THE INVENTION A principal object of the invention is toprovide a process permitting a direct synthesis, without ion exchange,of a pure faujasite containing both Li+ and Na+ cations and having thefollowing composition:

x ranging between 0.05 and 0.95.

Upon further study of the specification and appended claims, otherobjects and advantages of this invention will become apparent.

The direct synthesis of faujasite containing Na+ and Li+ presentsnumerous advantages because ion exchange reactions are generally longand arduous. Furthermore, aside from the omission of the ion exchangestep, it has been found that the direct synthesis of faujasitecontaining Li+ cations and Na+ cations is economically superior to thesynthesis of faujasite containing only Na+. In this connection, it hasbeen observed that faujasites can crystallize from amorphous mixtureshaving a lower Me O/Al O molar ratio (Me O being the total quantity ofwhen the amorphous mixtures contain both U 0 and Na O than when itcontains only Na O. Not only is the amount of basic oxide lowered, butalso the crystalline yield is increased when crystallizing faujasitefrom an amorphous mixture containing U 0 and Na O. Furthermore, forgiven Me O/Al O molar ratios and SiO A1 0 ratios in the amorphousmixture, the required crystallization time is decreased when the mixturecontains Li O.

According to the invention, the faujasite containing Na+ and Li+ cationsis crystallized at a temperature ranging between 20 and 105 C. from anamorphous crystallization mixture containing the oxides constitutingfaujasite having the molar ratios set forth in Table I.

TABLE I Molar ratios General range Preferred range TABLE II Molar ratiosGeneral range Preferred range Slog/A1203 1. 5-3 2-2. 5 (N 320 plusLiam/A1203 0. 8-3. 5 1-2. 8 75-300 100-200 HzQ/AlzOs A solution ofsodium or lithium silicate, water glass or meta-silicate can be used toprepare this first mixture, orinstead silica can be dissolved in sodiumor lithium hydroxide. The solution obtained is mixed, preferably withstirring, and at ordinary temperature, with a solution of sodiumaluminate in proportions corresponding to those given in Table 11 untilan homogeneous gel is obtained.

This gel can be immediately utilized without filtration, for thepreparation of the amorphous mixture. But it is preferably filtered,washed and dried at a temperature not exceeding 80 C. before being used.

The amorphous crystallization mixture is prepared by adjusting the gelto the limits defined in Table I. The SiO content is adjusted by adding,preferably at ordinary temperature, at least 0.5 mole of reactiveamorphous silica, based on one mole of A1 Generally amorphous silicahaving a particle size of less than 100 microns is added. Silica havinga higher particle size is generally not reactive enough, and faujasiteoften cannot be crystallized from the amorphous mixture. Silica having aparticle size less than 501/. is preferably used. The Na O and H 0contents are adjusted when necessary by adding water and sodiumhydroxide. Whereas the entire quantity of Li O necessary to adjust thecomposition (if any is necessary) is preferably introduced as lithiumhydroxide, a minor portion of this necessary quantity can optionally beintroduced by exchanging sodium ions in the gel. Practically, thequantity of Li O introduced by ion-exchange should not exceed 50% Asabove said, faujasite is crystallized from the amorphous crystallizationmixture at a temperature ranging between 20 and 105 C. At a temperatureof 20 C. it takes 8 to 60 days to obtain a well crystallized zeolite.Higher temperatures permit shorter crystallization times. Thus, 4 todays heating is necessary at 60 C. and 3 to 60 hours at 95 C. Whenperforming crystallization at a temperature higher than 30 C., theamorphous crystallization mixture is preferably maintained at atemperature of to 30 C. during 24 to 72 hours before heating at a highertemperature. Crystallization is preferably performed at a temperaturelower than 100 C. as at higher temperatures, other zeolites besidesfaujasite begin to crystallize. Furthermore, if the amorphous mixtureshave a high lithium content, for example, a content such that the molarratio LiO' /[LiO +Na O] is higher than 0.5, lithium rnetasilicate beginsto crystallize together with faujasite at a temperature higher than 80C. Therefore, in such cases crystallization is performed at atemperature not exceeding 80 C.

When the reaction is terminated, the crystallized precipitate isfiltered, washed with water until the wash water has a pH of 9 to 10,and dried, for example by heating at a temperature of 50 C.

The faujasite containing Li+ and Na+ is activated by heating attemperatures ranging between 200 and 600 C., preferably between 300 and350 C. under reduced pressure.

According to a preferred embodiment of the process of the invention afaujasite containing Li+ and Na+ cations is prepared having a SiO /Al 0molar ratio as high as possible for a given SiO /Al O molar ratio in theamorphous crystallization mixture. It is advantageous to obtain zeoliteshaving a high ratio SiO /Al O because they are more stable at hightemperatures and in acidic media.

This invention provides high silica contents, for it has been observedthat for a given Me O/AI O molar ratio (Me O being either Na O or NaO+Li O) in the amorphous mixture, the resultant crystallized faujasitewill have a higher silica content if the amorphous mixture contains Li Oand Na o than if the mixture contains only Na O. For example, incomparative tests two amorphous mixtures were heated at 100 C. during 72hours under the same conditions. The first mixture had the followingcomposition:

2.4Na O; A1 0 6510 150H O and the second one 2.4(0.8Na O:0.2Li O'); Al O6SiO 150H O In the first case, a faujasite containing only Na+ andhaving a SiO /Al O molar ratio equal to 3.90 was obtained and in thesecond case a faujasite containing Na+ and Li+ and having a SiO /Al Omolar ratio of 4.30 was obtained. This unexpected increase in the SiO A10 molar ratio is most noticeable for the lowest lithium contents, i.e.for LiO /(Na O+LiO) ratio equal to or slightly superior to 0.05.

Furthermore, it has been found that using amorphous mixtures in whichthe molar ratio Li O/Me O' is between 0.05 and 0.5 and the molar ratio HO/Al O is between and 200, faujasites can be crystallized from weaklybasic amorphous mixtures i.e., from mixtures in which the molar ratio Mo/A1 0, is low. Under such conditions there is for each molar ratio ofSiO /Al O in the amorphous mixture a minimum molar ratio of Me O/Al O asfollows:

TABLE in Molar ratio SiO /AI O For intermediate molar ratios of SiO /AlO the corresponding minimum molar of Me O/Al O can be obtained byinterpolation. As known, fajasites having the highest siO /Al o ratiosare precipitated from the least basic amorphous mixtures. It istherefore possible by adjusting the ratio of Me O/Al O as a function ofthe ratio of SiO /Al O to control the silica content of the faujasitecontaining Na+ and Li i.e., use the minimum value of Me O/Al O It mustbe noted, however, that for a molar ratio of SiO /Al O higher than 1-0the minimum value of M o/A1 0, in the amorphous mixture is already sohigh that there is practically no increase of the silica content of thefaujasite when the amorphous mixture contains Li O. On the other hand,at values of the SiO /Al O equal to or slightly above 2, the increase inthe silica content of the faujasite is the most significant.

To sum up, faujasites containing Li+ and Na+ having the highest silicacontents are crystallized from an amorphous mixture prepared accordingto the process of the invention having a molar ratio Li O/Me O comprisedbetween 0.05 and 0.5, a molar ratio HZO/AIZOQ comprised between 100 and200, and a minimum Me O/Al O' molar ratio corresponding to a given SiO/Al O molar ratio as given in Table III.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The following preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

EXAMPLE 1 A commercial solution of sodium silicate (16.4 g.) having thefollowing composition (in weight percent) 25.7% SiO 7.35% Na O; 67.0% B0 is diluted with 35 cc. of water. Then the solution obtained is mixedwith a solution of sodium aluminate containing 3.6 g.

5 A1 5.0 g. Na O, and 47 g. H O. The resultant gel has the followingcomposition (in molar ratios):

Slo /A1 0 2 Na O/Al O 2 8 H2O/Al2o3 140 After adding 23.5 g. ofamorphous reactive silica in powdered form and 4.2 g. of lithiumhydroxide LiOH-H O, the molar ratios in the gel become:

SiO /A1 O 12 0.2 A1203 7 H O A1 0 145 The mixture is heated at 95 C. for18 hours without stirring. After filtration, washing and drying, azeolite is obtained, having an X-ray diffraction diagram as shown inTable IV which when compared to natural calcium faujasite proves that itis also a faujasite.

After dehydration, the faujasite has the following com position:

It adsorbs 34.2% of water under a partial pressure of water of 13.5 mm.Hg at 25 C.

Norm-Intensity, I/L, symbols: vS=very strong, S=strong, 1118: medium tostrong, m=medium, mw=mednm1 to weak, w=weak, vw=very weak.

EXAMPLE 2 A sodium aluminosilicate gel is prepared by agitating: (1) asodium silicate solution containing 230 g. of amorphous hydrated silicawith 10.4% SiO 70 g. of sodium hydroxide and 2.1 l. of water, with (2) asolution of sodium alurninate containing 180 g. A1 0 230 g. Na O and2.3 1. of water.

The gel is filtered, washed with water and dried at 30 C. It has thefollowing composition (by weight):

Percent Si0 32.9 2 3 22.6 NagO 15.1 H O 28.6

corresponding to the following molar ratios:

SiO /Al 0 2.4 Na O/ A1203 1.]. H O/AI O 7.2

By mixing 11.3 g. of this gel with 4.2 g. of amorphous reactive silicahaving a particle size lower than 5011., 40 g. of water, 13 cc. of a Nsodium hydroxide solution 6 and 16 cc. of 5 N lithium hydroxide, a newgel having the following molar ratios are obtained:

A1203 5 Li O/ (Li q+Na 0.4 (Na O+Li O)/AI O 4 H20/ A1 0 150 This mixtureis maintained at a temperature of 60 C. for 12 days in a closed Pyrexflask. After filtration, washing and drying, the dehydrated faujasite(Li-Na) obtained has the following composition based on 1 mol of A1 0 Inthe anhydrous state this faujasite adsorbs 19.9% of nhexane at 25 C.under a partial pressure of n-hexane of 102 mm. Hg.

EXAMPLE 3 By adding 4.2 g. of amorphous reactive silica, 10 cc. ofwater, 45 cc. of a solution of a 5 N sodium hydroxide and 14 cc. of asolution of a 5 N lithium hydroxide to 11.3 g. of a sodiumaluminosilicate gel prepared as in Example 2, there is obtained amixture having the following composition (in molar ratios):

SiO A1 0 5 Li O/ (Li Of+-Na O) 0.2 /A12O3 7 H O/ A1 0 150 The mixture ismaintained at a temperature of 30 C. for 15 days and it is thereafterfiltered, washed with water and dried. The faujasite (Li-Na) thusobtained has the following composition (in molar ratios):

In the dehydrated state it adsorbs 16.4% of n-hexane at 60 C. under apartial pressure of 1 02 mm. Hg.

EXAMPLE 4 In 11.3 g. of sodium aluminosilicate prepared as described inExample 2, Na+ cations are exchanged against Li+ cations by contactingthe gel 4 times during one hour with an aqueous solution of 2 N LiCl.The ratio in the gel is equal to 0.89 and ratio (Li O+Na O)/Al O remainsequal to 1.1. By adding to this exchanged gel a lithium hydroxidesolution and amorphous reactive silica, an amorphous mixture is obtainedin which the molar ratios are as follows:

sio /Ai o, s H2O/A12O3 15o (Na O+Li O)/A1 O 3 The amorphous mixture isleft to stand at ambient temperature for 24 hours and is then heatedwithout agitation at 60 C. for 60 hours. It is filtered, washed withwater until a pH lower than 8 is obtained, and dried at C.

The faujasite Na-Li obtained has an X-ray diffraction diagram analogousto the diagram given in Table IV. Its molar chemical composition afterdehydration is as follows:

0.08Na O; 1.10Li O; A1 0 4.5Si0

EXAMPLE 5 In a first experiment, the following amorphous mixture inmols:

2.6Na O; A1 0 7SiO ISOH O was heated at C. for hours without anycrystallization taking place. Crystallization could only be obtainedwith an amorphous mixture containing 2.9Na O instead of 2.6Na O.

2.6(0.8'Na O.2Li O); A1 7810 150H O After 80 hours, a faujasite having ahigh degree of crystallinity and a molar ratio SiO /Al O of 4.50 wasprecipitated. These comparative tests show clearly that in the presenceof M 0 in the amorphous mixture, faujasite crystallizes from amorphousmixtures having a lower Me O/Al O ratio.

EXAMPLE 6 In a first experiment, 24.58 kg. of sodium hydroxide (76% NaO) was dissolved in 79.5 1. of water. Into the resultant solution therewas dissolved 22.68 kg. sodium aluminate (30.4% of Na O and 46.5 A1 0under heat and agitation. After being cooled at ambient temperature, asuspension of colloidal silica containing 30% SiO was added thereto, anda gel was obtained having the following molar composition:

4Na O; A1203; After crystallization, 36.3 kg. of a hydrated faujasitehaving the following molar composition was obtained:

4Na O; A1203; The yields based on the starting materials (by weight)were as follows:

were prepared according to Example 2 by mixing 7.82 kg. of sodiumaluminate (A1 0 39%; Na O: 33%), 12.7 kg. sodium silicate (SiO 28.3%; NaO: 6.8%; H 0: 64.9%) and 92.5 liters of Water.

To this gel, there were added 9 kg. of activated silica (81.1% by weightSiO 2.20 kg. NaOH and 1.09 kg. LiOH:H O (35% by weight Li O).

After crystallization, 14.20 kg. of hydrated faujasite having thefollowing molar composition was obtained:

The yields based on the starting material (by weight) were thefollowing:

Percent Anhydrous material 5 8 Na O 25 Li O 3 1 A1 0 76.5 SiO 64.0

It can be seen that the yields are higher when the amorphous mixturecontains Li O, than when it contains only N320.

EXAMPLE 7 In a first experiment, there is heated at 100 C. an amorphousmixture having the following molar composition:

2.4Na O; A1203; After 66 hours of heating, a faujasite crystallizedhaving a SiO /Al O ration of 3.90.

In a second experiment, an amorphous mixture having the following molarcomposition:

is heated at 100 C. under the same conditions. The faujasitecrystallized after only 48 hours and has a SiO A1 0 ratio of 4.50,proving that the addition of Li O results in faster crystallization timeand higher silica contents.

EXAMPLE 8 1st experiment An amorphous mixture was prepared as in thesecond experiment of Example 6. The mixture had the followingcomposition After hours heating at C., there was obtained a faujasitehaving a SiO/Al O ratio of 4.50.

2nd experiment An amorphous mixture having the following composition:

3.2(0.8Na O; 0.2Li O); A1 0 9SiO ISOH 'O was prepared under the sameconditions as the first experiment. After 90 hours of heating at 95 C.,there was obtained a faujasite having a SiO /AI O ratio of 5.10.

3rd experiment An amorphous mixture having the following composition:

prepared under the same conditions.

The mixture was heated at 95 C. and after 120 hours of heating there wasobtained a faujasite having a SiO A1 0 ratio of 560.

4th experiment There was prepared an amorphousmixtureunder the sameconditions having the following composition:

3.0(0.8Na O; 0.2Li O); A1203; 9SiO 15011 0 No faujasite could becrystallized by heating at 95 C. after 60 days.

The preceding examples can be repeated with similar success bysubstituting the generally or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

What is claimed is:

1. A process for the preparation of a face-centered cubic faujasitecontaining sodium and lithium cations, comprising:

(a) forming an aluminosilicate gel of the following composition andcontaining the total quantity of alumina necessary for said faujasite:

SiO /Al O 1.5 l-3 :1 (Na O+Li O) /Al O 0.08: 13.5:1 H O/ A1 0 75: 1-300:1

(b) adjusting the SiO Na O, Li O and H 0 content of this first gel toobtain an amorphous mixture of the following composition:

Sim/A1 0 2: 1-16 :1 (Na- 0+Li O) /Al203 1.45:1-8: 1 Lip/(Na O+Li 0)0.05;1-0.9s:1 H O/ A1 0 75 1-30011 the SiO content being adjusted byadding at least 0.5 mole of reactive silica, having a particle size ofless than microns, per 1 mole of A1 0 and (c) precipitating from saidamorphous mixture at a crystallization temperature of 20 to C. acrystallized precipitate of faujasite.

Slo /A1 Minimum (Li O +Na O) A1 0 1.45

3. A process according to claim 1 wherein the amorphous mixture isheated at a crystallization temperature of 20 to 100C. to obtain acrystallized precipitate of faujasite.

4. A process according to claim 2 wherein the amorphous mixture isheated at a crystallization temperature of 60 to 100 C.

5. A process according to claim 1 wherein the amorphous mixture has acomposition such that the ratio Li O/ [Na O-l-Li o] is higher than 0.5and the amorphous mixture is heated to a temperature not exceeding 80 C.to obtain a crystallized precipitate of faujasite.

6. A process according to claim 1 wherein the first gel is prepared byadding a solution selected from the group consisting of sodium silicate,lithium silicate, and mixtures thereof to an aqueous solution of sodiumaluminate.

7. A process according to claim 1 wherein the Li O content of theamorphous mixture is adjusted by adding lithium hydroxide.

8. A process according to claim 1 wherein the U 0 content of theamorphous mixture is partially adjusted by ion exchange.

9. A process according to claim 1 wherein the molar ratio of SiO /A1 Ois adjusted by adding silica having a particle size less than 50microns.

10. A process according to claim 1 wherein the amorphous mixture ismaintained at a temperature of 20 to 30 C. for 24 to 72 hours and thenheated to a crystallization temperature higher than 30 C.

11. A process as defined by claim 1, the molar ratio of the gel in step(a) being:

10 SiO A1 0 2: l-2.5 1 (Nil O-l-Li O) /Al O l:12.8 :1 H2O/Al203 1200: 1

12. A process as defined by claim 1, the molar ratio of the amorphousmixture in step (b) being:

Slog/A1203 2:1-1011 (Na O-!Li O)/A1 O 1.45 21-35 :1 Li O/(Na O+Li O)0.05:1-0.5:1 H20/Al203 100:1-20021 13. A process as defined by claim 1wherein all of the Li O required to produce the faujasite is added instep (b).

14. A process as defined by claim 1 wherein at least a portion of the LiO required for the faujasite is incorporated in gel in step (a).

15. A process for the preparation of a face-centered cubic faujasitecontaining sodium and lithium cations, comprising:

(a) crystallizing at 20-l05 C. said faujasite from an amorphous mixtureof an aluminosilicate gel admixed with amorphous silica having aparticle size of less than 100 microns, said amorphous mixture having atleast 0.5 mole of said amorphous silica per mole of A1 0 in the gel,said gel having the following compositions:

SiO /Al O 1.5:1-3:1 (NaO+Li 0)/Al O 0.0s;1 3.s=1 r o/A1 0, 7s=1-30o:1

said A1 0 in the gel being the total quantity of alumina necessary forsaid faujasite, said amorphous mixture having the following molarratios:

References Cited UNITED STATES PATENTS 12/ 1968 Ciric 423329 X 3/1968McDaniel et a1 423329 1/1970 Jenkins 423329 5/1970 Hindin et al. 423329EDWARD J. MEROS, Primary Examiner UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3 798 311 Dated March 19 1974lnventofls) Jean-Louis GUTH, et a1.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

IN THE CLAIMS:

CLAIM 2, COLUMN 9, LINE 4: (Li O+NaO) should read (Ll om o) Signed andsealed this 13th day of August 1974 (SEAL) Attest:

MCCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents F R po'wso ($69) USCOMM-DC 60376-P69 t U.S. GOVERNMENT PRINTINGOFFICE: I969 0-366-334,

